As a rotation detecting device of this kind, the rotation detecting device is known, which utilizes a winding stator and a rotor and in which a plurality of tracks having different numbers of poles are formed in the rotor to thereby form an absolute encoder so that the absolute angle can be detected in reference to the phase difference in signals detected from those tracks. (See, for example, Patent Document 1 listed below.)
As another rotation detecting device, that obtains two phase magnetic field signals has been suggested. (See, for example, Patent Document 2 listed below.) This is provided with a magnetic pulse generating means of a ring shape such as, for example, a magnetic encoder, in which magnetic pole pairs are arranged in a circumferential direction, for generating magnetic pulses, and a plurality of detecting elements arranged in a circumferential direction relative to this magnetic pulse generating means for detecting the magnetic pulses, the absolute angle being detected by calculating respective output signals of the detecting elements.
Also, as a further rotation detecting device, there has been suggested a device in which a mode for outputting the absolute angle is executed by the utilization of the ABZ phase signal. (See, for example, Patent Document 3 listed below.)
As a still further rotation detecting device, there has been suggested a device, which utilizes a plurality of rows of magnetic encoders, of which numbers of poles are different from each other, and in which by the utilization of a plurality of magnetic sensors capable of detecting the respective magnetic fields of those magnetic encoders, the absolute angle can be calculated in reference to the phase difference between the magnetic signals detected by those magnetic sensors. (See, for example, Patent Documents 4 listed below.)                [Patent Document 1] JP Laid-open Patent Publication No. 2006-322927        [Patent Document 2] JP Published Int'l Application No. 2002-541485        [Patent Document 3] JP Laid-open Patent Publication No. 2008-116291        [Patent Document 4] JP Laid-open Patent Publication No. 2008-233069        